Professor Brian Cox and Dara O Briain have packed their sunscreen and headed to Australia to gaze up at a sky that will be completely unfamiliar to viewers in the UK - packed full of the most astonishing features from constellations like the Southern Cross, famously featured on Australia's flag, to jewel-like clusters of stars and perfectly positioned planets. But capping it all is the most remarkable view of the Milky Way, arching overhead like a river of stars.